In “Deployment of a rapidly re-deployable HF radar concept”, T. M. Blake, Electro-Magnetic Remote Sensing (EMRS) Defence Technology Centre (DTC) 1st Annual Technical Conference 20-21st May 2004, there is disclosed an HF surface wave radar system as shown in FIG. 1, comprising a linear array of separate spaced apart (7 meter spacing) receive antenna elements 2, each element being a vertical active antenna, 2.5 meters long. Each element includes a receiver 4 for processing received signals. The elements are connected in a daisy chain arrangement by digital data link cables 6 to a control centre 8, shown located in a van. A corresponding transmit antenna array 9 is also provided. The system is taken to a site in a disassembled state in the van, and then rapidly assembled by two technicians by placing the elements in the ground in spaced apart positions, and connecting them together by the data link cables.
By placing receivers at the base of the elements, difficulties arise in that the elements have to be synchronised in time, frequency and phase in order that the radar system function accurately. Further their position relative to one another needs to be known accurately, but since they are positioned by hand by technicians without scientific instruments to permit accurate placement, (desirably to within 0.1 meters) this is a further problem.
Whilst a wide variety of HF antenna arrays are known comprising a multiplicity of antenna elements, such elements are normally fixedly mounted together in a framework or other mounting arrangement—this would not be suitable for a rapidly deployable system, in particular where the elements are spaced a long distance apart.